Synthesis, structural and magnetic studies of imidazolium bis(oxalato)cuprate(II)

Synthesis, X‐ray Crystal Structure and Magnetic Properties of Oxalato‐Bridged Copper(II) Complexes with 2,3‐Bis(2‐pyridyl)pyrazine, 2,3‐Bis(2‐pyridyl)quinoxaline and 2,2′‐Bipyrazine as Peripheral Ligands

“…Looking at the different intrachain out‐of‐plane exchange pathways occurring in 3 , [Cu(1)O(1)O(1a)Cu(1a) and Cu(1)O(2)C(10)O(3)O(3b)C(10b)O(2b)Cu(1b)], most likely the strongest antiferromagnetic interaction ( J = −1.44 cm −1 ) corresponds to the shorter pathway (double oxalate− oxygen bridge) whereas the weakest one (α J = −0.69 cm −1 ) is ascribed to the longer pathway. Concerning the significance of these coupling values, it should be noted that: (i) weak antiferromagnetic interactions between copper( II ) ions through double oxalate−oxygen bridge were observed in the complexes H 2 Im[Cu(ox) 2 ] (Him = imidazole, J = −1.09 cm −1 )2e and Na 2 [Cu(ox) 2 ]·2H 2 O ( J = −1.2 cm −1 ),2b and (ii) either weak antiferro‐ or ferromagnetic interactions were reported for the copper( II ) complexes M 2 [Cu(ox) 2 ]·2H 2 O [M = K + ( J = −0.7 cm −1 ) and NH 4 + ( J = −0.6 cm −1 )],2a [Cu(pyim)(H 2 O)(ox)]·2H 2 O [pyim = 2‐(2‐pyridyl)imidazole, J = +0.04 cm −1 ]18 and [Cu(H 2 bim)(H 2 O)(ox)]·H 2 O [H 2 bim = 2,2′‐biimidazole, J = −0.08]18 where the longer out‐of‐plane exchange pathway occurs.…”

Synthesis, X‐ray Crystal Structure and Magnetic Properties of Oxalato‐Bridged Copper(II) Complexes with 2,3‐Bis(2‐pyridyl)pyrazine, 2,3‐Bis(2‐pyridyl)quinoxaline and 2,2′‐Bipyrazine as Peripheral Ligands

“…Looking at the different intrachain out‐of‐plane exchange pathways occurring in 3 , [Cu(1)O(1)O(1a)Cu(1a) and Cu(1)O(2)C(10)O(3)O(3b)C(10b)O(2b)Cu(1b)], most likely the strongest antiferromagnetic interaction ( J = −1.44 cm −1 ) corresponds to the shorter pathway (double oxalate− oxygen bridge) whereas the weakest one (α J = −0.69 cm −1 ) is ascribed to the longer pathway. Concerning the significance of these coupling values, it should be noted that: (i) weak antiferromagnetic interactions between copper( II ) ions through double oxalate−oxygen bridge were observed in the complexes H 2 Im[Cu(ox) 2 ] (Him = imidazole, J = −1.09 cm −1 )2e and Na 2 [Cu(ox) 2 ]·2H 2 O ( J = −1.2 cm −1 ),2b and (ii) either weak antiferro‐ or ferromagnetic interactions were reported for the copper( II ) complexes M 2 [Cu(ox) 2 ]·2H 2 O [M = K + ( J = −0.7 cm −1 ) and NH 4 + ( J = −0.6 cm −1 )],2a [Cu(pyim)(H 2 O)(ox)]·2H 2 O [pyim = 2‐(2‐pyridyl)imidazole, J = +0.04 cm −1 ]18 and [Cu(H 2 bim)(H 2 O)(ox)]·H 2 O [H 2 bim = 2,2′‐biimidazole, J = −0.08]18 where the longer out‐of‐plane exchange pathway occurs.…”

Step by step crystal-to-crystal transformation from 1D K 2 Cu(C 2 O 4 ) 2 (H 2 O) 4 (1) to 1D K 2 Cu(C 2

“…From the chained structure, the data were fitted with the S = 1/2 isotropic Heisenberg chain and it obtained the best fit of J = −0.0509IJ3) cm −1 , g = 2.154(2), and R = 6.25 × 10 −5 for 1 (2-200 K); J = −0.059IJ2) cm −1 , g = 2.24, and R = 5.95 × 10 −5 for 2 and J = 0.064(2) cm −1 , g = 2.130(1), and R = 3.80 × 10 −5 for 3 from 2 to 300 K. This corresponds with the structural analysis, where the Cu-O distance between two CuIJC 2 O 4 ) 2 2− units in 2 is shorter than in 1 and 3; therefore, the antiferromagnetic interaction, which is always stronger than the ferromagnetic interaction, is observed. 5,8 The isothermal magnetization saturates about 1 Nβ at 2 K of 1-3 (Fig. S7 †…”

Imidazoliumtrans-bis(iminodiacetato-κ3O,N,O′)cobaltate(III)

“…For hydrogen bonds in related compounds containing imidazolium, see: Allen (2002); Chattopadhyay et al (1995); Gao et al (2009); Hsu & Schlemper (1980); Rissanen & Pursiainen (2000). Bifurcated hydrogen bonds were discussed by Jeffrey et al (1985).…”

“…Interestingly, this type of hydrogen bond in imidazolium compounds was found in a search of the Cambridge Structural Database (CSD version 5.30; Allen, 2002). Among the 200 hits for imidazolium compounds, there are only seven compounds having the similar bifurcated hydrogen bonds (C-H from imidazolium), namely, imidazolium hydrogen maleate (Hsu & Schlemper, 1980), benzo-18-crown-6 imidazolium clathrate perchlorate (Rissanen & Pursiainen, 2000), bis(imidazolium) bis(oxalato-O,O′)copper(II) (Chattopadhyay et al, 1995). Their distances of H•••O are in the range of 2.10 to 2.49 Å.…”

Synthesis, X‐ray Crystal Structure and Magnetic Properties of Oxalato‐Bridged Copper(II) Complexes with 2,3‐Bis(2‐pyridyl)pyrazine, 2,3‐Bis(2‐pyridyl)quinoxaline and 2,2′‐Bipyrazine as Peripheral Ligands

“…Looking at the different intrachain out‐of‐plane exchange pathways occurring in 3 , [Cu(1)O(1)O(1a)Cu(1a) and Cu(1)O(2)C(10)O(3)O(3b)C(10b)O(2b)Cu(1b)], most likely the strongest antiferromagnetic interaction ( J = −1.44 cm −1 ) corresponds to the shorter pathway (double oxalate− oxygen bridge) whereas the weakest one (α J = −0.69 cm −1 ) is ascribed to the longer pathway. Concerning the significance of these coupling values, it should be noted that: (i) weak antiferromagnetic interactions between copper( II ) ions through double oxalate−oxygen bridge were observed in the complexes H 2 Im[Cu(ox) 2 ] (Him = imidazole, J = −1.09 cm −1 )2e and Na 2 [Cu(ox) 2 ]·2H 2 O ( J = −1.2 cm −1 ),2b and (ii) either weak antiferro‐ or ferromagnetic interactions were reported for the copper( II ) complexes M 2 [Cu(ox) 2 ]·2H 2 O [M = K + ( J = −0.7 cm −1 ) and NH 4 + ( J = −0.6 cm −1 )],2a [Cu(pyim)(H 2 O)(ox)]·2H 2 O [pyim = 2‐(2‐pyridyl)imidazole, J = +0.04 cm −1 ]18 and [Cu(H 2 bim)(H 2 O)(ox)]·H 2 O [H 2 bim = 2,2′‐biimidazole, J = −0.08]18 where the longer out‐of‐plane exchange pathway occurs.…”

Step by step crystal-to-crystal transformation from 1D K 2 Cu(C 2 O 4 ) 2 (H 2 O) 4 (1) to 1D K 2 Cu(C 2

“…From the chained structure, the data were fitted with the S = 1/2 isotropic Heisenberg chain and it obtained the best fit of J = −0.0509IJ3) cm −1 , g = 2.154(2), and R = 6.25 × 10 −5 for 1 (2-200 K); J = −0.059IJ2) cm −1 , g = 2.24, and R = 5.95 × 10 −5 for 2 and J = 0.064(2) cm −1 , g = 2.130(1), and R = 3.80 × 10 −5 for 3 from 2 to 300 K. This corresponds with the structural analysis, where the Cu-O distance between two CuIJC 2 O 4 ) 2 2− units in 2 is shorter than in 1 and 3; therefore, the antiferromagnetic interaction, which is always stronger than the ferromagnetic interaction, is observed. 5,8 The isothermal magnetization saturates about 1 Nβ at 2 K of 1-3 (Fig. S7 †…”

Imidazoliumtrans-bis(iminodiacetato-κ3O,N,O′)cobaltate(III)

“…For hydrogen bonds in related compounds containing imidazolium, see: Allen (2002); Chattopadhyay et al (1995); Gao et al (2009); Hsu & Schlemper (1980); Rissanen & Pursiainen (2000). Bifurcated hydrogen bonds were discussed by Jeffrey et al (1985).…”

“…Interestingly, this type of hydrogen bond in imidazolium compounds was found in a search of the Cambridge Structural Database (CSD version 5.30; Allen, 2002). Among the 200 hits for imidazolium compounds, there are only seven compounds having the similar bifurcated hydrogen bonds (C-H from imidazolium), namely, imidazolium hydrogen maleate (Hsu & Schlemper, 1980), benzo-18-crown-6 imidazolium clathrate perchlorate (Rissanen & Pursiainen, 2000), bis(imidazolium) bis(oxalato-O,O′)copper(II) (Chattopadhyay et al, 1995). Their distances of H•••O are in the range of 2.10 to 2.49 Å.…”

Synthesis, X‐ray Crystal Structure and Magnetic Properties of Oxalato‐Bridged Copper(II) Complexes with 2,3‐Bis(2‐pyridyl)pyrazine, 2,3‐Bis(2‐pyridyl)quinoxaline and 2,2′‐Bipyrazine as Peripheral Ligands

“…Looking at the different intrachain out‐of‐plane exchange pathways occurring in 3 , [Cu(1)O(1)O(1a)Cu(1a) and Cu(1)O(2)C(10)O(3)O(3b)C(10b)O(2b)Cu(1b)], most likely the strongest antiferromagnetic interaction ( J = −1.44 cm −1 ) corresponds to the shorter pathway (double oxalate− oxygen bridge) whereas the weakest one (α J = −0.69 cm −1 ) is ascribed to the longer pathway. Concerning the significance of these coupling values, it should be noted that: (i) weak antiferromagnetic interactions between copper( II ) ions through double oxalate−oxygen bridge were observed in the complexes H 2 Im[Cu(ox) 2 ] (Him = imidazole, J = −1.09 cm −1 )2e and Na 2 [Cu(ox) 2 ]·2H 2 O ( J = −1.2 cm −1 ),2b and (ii) either weak antiferro‐ or ferromagnetic interactions were reported for the copper( II ) complexes M 2 [Cu(ox) 2 ]·2H 2 O [M = K + ( J = −0.7 cm −1 ) and NH 4 + ( J = −0.6 cm −1 )],2a [Cu(pyim)(H 2 O)(ox)]·2H 2 O [pyim = 2‐(2‐pyridyl)imidazole, J = +0.04 cm −1 ]18 and [Cu(H 2 bim)(H 2 O)(ox)]·H 2 O [H 2 bim = 2,2′‐biimidazole, J = −0.08]18 where the longer out‐of‐plane exchange pathway occurs.…”

Step by step crystal-to-crystal transformation from 1D K 2 Cu(C 2 O 4 ) 2 (H 2 O) 4 (1) to 1D K 2 Cu(C 2

“…From the chained structure, the data were fitted with the S = 1/2 isotropic Heisenberg chain and it obtained the best fit of J = −0.0509IJ3) cm −1 , g = 2.154(2), and R = 6.25 × 10 −5 for 1 (2-200 K); J = −0.059IJ2) cm −1 , g = 2.24, and R = 5.95 × 10 −5 for 2 and J = 0.064(2) cm −1 , g = 2.130(1), and R = 3.80 × 10 −5 for 3 from 2 to 300 K. This corresponds with the structural analysis, where the Cu-O distance between two CuIJC 2 O 4 ) 2 2− units in 2 is shorter than in 1 and 3; therefore, the antiferromagnetic interaction, which is always stronger than the ferromagnetic interaction, is observed. 5,8 The isothermal magnetization saturates about 1 Nβ at 2 K of 1-3 (Fig. S7 †…”

Imidazoliumtrans-bis(iminodiacetato-κ3O,N,O′)cobaltate(III)

“…For hydrogen bonds in related compounds containing imidazolium, see: Allen (2002); Chattopadhyay et al (1995); Gao et al (2009); Hsu & Schlemper (1980); Rissanen & Pursiainen (2000). Bifurcated hydrogen bonds were discussed by Jeffrey et al (1985).…”

“…Interestingly, this type of hydrogen bond in imidazolium compounds was found in a search of the Cambridge Structural Database (CSD version 5.30; Allen, 2002). Among the 200 hits for imidazolium compounds, there are only seven compounds having the similar bifurcated hydrogen bonds (C-H from imidazolium), namely, imidazolium hydrogen maleate (Hsu & Schlemper, 1980), benzo-18-crown-6 imidazolium clathrate perchlorate (Rissanen & Pursiainen, 2000), bis(imidazolium) bis(oxalato-O,O′)copper(II) (Chattopadhyay et al, 1995). Their distances of H•••O are in the range of 2.10 to 2.49 Å.…”